Copper is widely used for many industrial applications because of the excellent processing characteristic and high thermal and electric conductivity thereof. Copper ion is one of the essential elements for various living organisms. However, the concentration of the copper ion increases through the industrial utilization, causing serious toxicity to the living organisms. Moreover, when other heavy metals such as cadmium and mercury are absorbed in body systems, itai-itai disease and Minamata disease may be generated, respectively. Accordingly, many researchers have been studied on the fabrication of metal ion sensors for the easy detection of heavy metals. However, the conventional metal ion sensors are operated in non-pure water i.e. in organic solvent or mixed solution of water and organic solvent due to the solubility of the sensing materials. Furthermore, the quantitatively analysis of metal ions can be hardly occurred without using spectroscopic equipments and the detecting speed of the sensor is slow, resulting in a limitation to practical applications thereof.